The dependence of high-temperature oxidation and the thermal shock resistance behavior of alpha-SiC coated nuclear-grade graphite substrates were investigated at elevated temperatures. The surfaces of three kinds of nuclear-grade graphite substrates were coated with alpha-SiC by chemical vapor reaction (CVR) at a temperature of 1600 degrees C and a pressure of 1.3 Pa in a pure polysilicon gas atmosphere. Thermal shock and oxidation resistance tests were performed at 1000 degrees C and 1300 degrees C respectively, in which the samples were taken out of a box furnace and directly exposed to air at room temperature. It was found that the initial microstructure of the graphite substrates plays an important role in determining the final thermal properties of the alpha-SiC coatings when using the CVR method.

Keywords: SiC; Coating; CVR; Oxidation; Thermal shock; Microstructure